From d24207a0d81cee81d0f06397074db99e12cc87c1 Mon Sep 17 00:00:00 2001 From: James Morse Date: Tue, 18 Oct 2016 11:27:47 +0100 Subject: [PATCH] arm64: mm: Set PSTATE.PAN from the cpu_enable_pan() call commit 7209c868600bd8926e37c10b9aae83124ccc1dd8 upstream. Commit 338d4f49d6f7 ("arm64: kernel: Add support for Privileged Access Never") enabled PAN by enabling the 'SPAN' feature-bit in SCTLR_EL1. This means the PSTATE.PAN bit won't be set until the next return to the kernel from userspace. On a preemptible kernel we may schedule work that accesses userspace on a CPU before it has done this. Now that cpufeature enable() calls are scheduled via stop_machine(), we can set PSTATE.PAN from the cpu_enable_pan() call. Add WARN_ON_ONCE(in_interrupt()) to check the PSTATE value we updated is not immediately discarded. Reported-by: Tony Thompson Reported-by: Vladimir Murzin Signed-off-by: James Morse [will: fixed typo in comment] Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- arch/arm64/mm/fault.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index d4634e6942ca..247bae758e1e 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -29,7 +29,9 @@ #include #include #include +#include +#include #include #include #include @@ -608,7 +610,14 @@ asmlinkage int __exception do_debug_exception(unsigned long addr, #ifdef CONFIG_ARM64_PAN int cpu_enable_pan(void *__unused) { + /* + * We modify PSTATE. This won't work from irq context as the PSTATE + * is discarded once we return from the exception. + */ + WARN_ON_ONCE(in_interrupt()); + config_sctlr_el1(SCTLR_EL1_SPAN, 0); + asm(SET_PSTATE_PAN(1)); return 0; } #endif /* CONFIG_ARM64_PAN */ -- 2.20.1